1. Field of the Invention
The invention relates to development and preservation of living water resources and is directed more particularly to a method for preserving and encouraging development of aquatic species, such as fish, turtles, large invertebrates (such as shrimp, prawns, and lobsters), and other aquatic species that travel through freshwater estuaries, and other marine environments.
2. Description of the Prior Art
Sustainable water resources development is facilitated by the use of hydraulic structures to: 1) pass adult fish around dams or other channel obstructions so they can migrate to their historical spawning and nursery areas, 2) pass juvenile fish around channel obstructions to their adult habitat areas, and 3) physically exclude fish from turbine, pump, or dredge intakes where they can be injured or killed. Methods presently used to design, site, and operate these structures are inadequate for many applications.
The design of hydraulic structures for fish passage and protection typically involves the selection and implementation of a number of design elements in order to develop the fully operational system. Hydraulically-based fish passage structures typically include varying designs of components, such as diversion screens, orifices, fish ladders, surface collectors, navigation locks, and other structures whose primary or secondary function is to facilitate movement of fish around a dam or other channel obstruction. Fish protection devices include physical exclusion structures, behavioral devices using light and sound, and special operating techniques for hydraulic structures whose mere existence potentially influences the behavior of fish. Fish protection structures are typically used to prevent fish entry into hydroturbines, irrigation intakes, and dredge heads. Once a system is designed, it must be optimally sized, sited, and operated for maximum efficiency. Currently, methods available to aid selection of design alternatives are relatively crude. Methods for integrating design elements into a complete fish passage or protection system are nonexistent or merely anecdotal, and there is little available for optimal siting of the structures and their operation.
Hydraulic structures for fish passage and protection are currently designed by combining assumptions, or criteria, of fish behavior with bulk flow characteristics of the hydraulic flow field, as predicted by mathematical hydraulic models, measured in scaled physical hydraulic models, or measured at existing structures. Model-predicted or measured hydraulic data are integrated with these assumptions, or criteria, to design structures that will pass fish around obstructions in rivers and lakes, or prevent their entry into hydro-turbines, pumps, dredges, or other mechanical structures that can injure or kill them. Unfortunately, systematic application of these assumptions and criteria does not guarantee that efficient designs, sites, or operations will be identified and selected. Numerous unsuccessful fish passage and protection structures, costing many millions of dollars, have been constructed. The inefficiency of the design process, coupled with the endangered or threatened status of many fish species, requires that the present qualitative process of designing fish passage and protection technologies be considerably improved to insure the protection and restoration of the nation's aquatic natural resources. In addition, because presently used methods are qualitative, they cannot be easily included into population, community, water quality, or ecosystem models that are typically used to predict and evaluate the environmental consequences of different fish passage and protection strategies.
The literature available to describe the response of fish to flow fields is dominated by the reliance of studies on simple stream gaging methods for describing the position of fish in hydraulic nets. That is, the position of the fish is described in terms of velocity and depth at the point of measurement, or as an average of cell velocity and cell depth. Unfortunately, this type of hydraulic characterization for habitat description and modeling is insufficient to capture the complexity of fish behavior in complicated hydraulic fields.
The success of fish passage hydraulic structures must be based on the creation of hydraulic patterns that: 1) attract fish to optimal areas for passage, 2) induce fish to enter into the fishway structure, 3) encourage fish to successfully pass through the structure, 4) create exit conditions that prevent fish from loitering in the fishway, and 5) discourage fish from turning in the wrong direction after they depart from the fishway. The state-of-the-art provides no quantitative method for selecting from competing designs to achieve steps 1-5 above. The success of fish protection hydraulic structures must be based on the creation of hydraulic patterns that discourage fish from entering regions of the hydraulic structure where they can be injured or killed and/or prevent and minimize their physical impact with a protection device.
The lack of systematic success and, in some cases, the failure of fish passage and protection structures, prove that guiding concepts employed to design such structures must be significantly enhanced. Evaluation of the prior art design process for fish passage and protection structures indicates that a major source of uncertainty occurs in the qualitative or anecdotal methods used to relate fish behavior to predicted or measured hydraulic fields. Therefore, fish behavior is not rigorously included in the design selection process for fish passage and fish protection systems. It is enticing to apply anthropomorphic logic to bulk flow patterns as the basis for selecting design alternatives because the flow patterns can be easily visualized in plan view in physical models and in plan view or profile view in mathematical hydraulic models. Unfortunately, the information content of bulk flow patterns that are so obvious to researchers observing physical models or inspecting the output of mathematical hydraulic models is not available to fish because of the limitations and capabilities of fish sensory systems. Fish are embedded in the fluid medium and are much more likely to utilize or be restricted to the information they can acquire in their immediate hydraulic surrounding as they select a swim path through the complex hydraulic and acoustic environment generated by fish protection and passage structures. Fish may be completely unaware of the overall hydraulic pattern because the large-scale bulk flow pattern so obvious to engineers and biologists when visualizing flow fields, is unavailable to organisms imbedded in the fluid medium.
There is thus a need for a method for designing fish passageways, which method integrates several technologies, to optimally design, locate, and operate fish passage and protection structures, and which includes fish behavior in the design of hydraulic structures used to pass or protect fish and other aquatic organisms.